A sensor (200) includes a sensor element (10), a tubular metallic shell (138), and a tubular mounting member (180) rotatable relative to the metallic shell. The metallic shell has a body (138a) and a flange (138f) provided forward of the mounting member and projecting radially outward beyond the radially inner surface of the mounting member. Further, the radially outer surface of the body and the rearward-oriented surface of the flange are connected by a slant surface (138t). The mounting member is such that a forward-oriented surface (180a) and a radially inner surface (180b) meet at a corner (180e). When a threaded portion (180s) of the mounting member is threadingly engaged with a mounting hole (300h) of a mount body (300), a forward-oriented surface (138f1) of the flange comes into contact with a mounting surface (300r) of the mount body, and the corner comes into contact with the slant surface.